JP5431610B1 - Base station, interference suppression device, and interference suppression method - Google Patents

Abstract

A base station, an interference suppression device, and an interference suppression method are provided that can suppress an interference signal generated by frequency conversion from a radio signal having a frequency band different from that of a radio signal received from a communication terminal.
When a radio signal in a first frequency band including a desired signal and a plurality of interference signals is received, the radio signal in the second frequency band before being converted into an interference signal in the first frequency band And frequency-converting the received signal in the second frequency band to generate a reference signal in the first frequency band. Based on the reference signal and the received signal in the first frequency band, a plurality of interference replica signals corresponding to the plurality of interference signals are generated. Here, the processing including the detection of the interference signal, generation of the interference replica signal, and suppression of the interference signal is continuously executed a plurality of times.
[Selection] Figure 14

Description

  The present invention relates to a base station capable of wireless communication with a communication terminal, an interference apparatus that can use the base station, and an interference suppression method.

  2. Description of the Related Art Conventionally, a base station that obtains good communication quality with a communication terminal by suppressing an interference signal included in a reception signal when receiving a radio signal transmitted from the communication terminal is known. For example, a base station that generates an interference replica signal from a known signal (for example, a pilot symbol in a CDMA system) and subtracts the generated interference replica signal from a received signal is known (see, for example, Patent Document 1). In this base station, it is possible to suppress interference signals from adjacent base stations and interference signals from communication terminals other than the reception request target existing in the same base station cell.

The interference signal suppressed by the conventional base station is an interference signal between the communication terminal and the base station, such as an interference signal from an adjacent base station or an interference signal from a communication terminal existing in the same base station cell. It is a radio signal transmitted and received in a radio communication network. For this reason, it is considered that interference signals can be suppressed using the above-described known signals (for example, pilot symbols in the CDMA system). However, the received signal received by the base station may include other interference signals that are difficult to predict other than the radio signals transmitted and received by the wireless communication network. Then, when this inventor investigated about such another interference signal, it turned out that the interference signal resulting from the radio broadcast wave transmitted from the broadcast satellite exists as shown below. In FIG. 20, since the frequency band of the radio broadcast wave d _RF from the broadcast satellite 90 is normally 11 GHz band, it is considered that there is no interference with the 1.5 GHz band radio signal x _MS transmitted from the communication terminal 80. It is done. However, the received signal (BS-RF signal) received by the BS receiving system 95 from the broadcasting wave d _RF from the broadcasting satellite 90 is basically frequency conversion incorporated in the receiving device 97 mounted on the parabolic antenna 96. A signal converted to an intermediate frequency (BS-IF) signal by an apparatus (LNB: Low Noise Block Converter) (hereinafter, a signal converted to an intermediate frequency (BS-IF) by the LNB is referred to as an LNB BS-IF signal). ), And transmitted to a broadcast receiver (not shown) via the coaxial cable 98. Further, the BS-IF signal by the LNB takes into account the transmission loss of the coaxial cable 98 and the distribution loss when the received signal is distributed in the apartment house, and the like, and the amplification device (booster) 99 provided near the antenna 96 is used. In some cases, the signal is amplified (hereinafter, the signal amplified by the booster 99 is referred to as “BS-IF signal by the booster”). BS-IF signal by the BS-IF signal and boosters by the LNB is in the 1.4GHz band of the same 1.5GHz band or the vicinity thereof and a radio signal _{x MS} to be transmitted to the base station 100 from the communication terminal 80. For this reason, if the radio wave shielding (shielding) of these devices 97 and 99 is insufficient or there is a connection error with the connector of the coaxial cable 98, the intermediate frequency signal xBS _-IF after frequency conversion is transmitted to the space as radio waves. It was found that the leaked radio wave was received by the base station 100 and became an interference signal.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a base capable of suppressing an interference signal generated by frequency conversion from a radio signal having a frequency band different from that of a radio signal received from a communication terminal. It is to provide a station, an interference suppression device, and an interference suppression method.

A base station according to the present invention is a base station capable of wireless communication with a communication terminal, and includes a first frequency band radio signal including a desired signal transmitted from the communication terminal and a plurality of interference signals that interfere with the desired signal. When receiving a radio signal in the first frequency band including the first receiving means for receiving the desired signal and a plurality of interference signals that interfere with the desired signal, the interference signal in the first frequency band Second receiving means for receiving a radio signal in the second frequency band before frequency conversion; and reference signal generating means for generating a reference signal in the first frequency band by frequency converting the received signal in the second frequency band. Detecting a plurality of interference signals included in the received signal of the first frequency band based on the reference signal and the received signal of the first frequency band, and corresponding to at least a part of the detected plurality of interference signals Multiple interference replica signals to generate The interference replica signal generating means suppresses a plurality of interference signals included in the received signal in the first frequency band by subtracting a plurality of interference replica signals corresponding to the plurality of interference signals from the received signal in the first frequency band. An interference suppression means for performing the processing including the detection of the plurality of interference signals, the generation of the plurality of interference replica signals, and the suppression of the plurality of interference signals a plurality of times in succession. A plurality of sets of replica signal generation means and interference suppression means are provided.
Further, the interference suppression apparatus according to the present invention generates an interference replica signal corresponding to an interference signal from a received signal in a first frequency band including a desired signal transmitted from a communication terminal and an interference signal that interferes with the desired signal. An interference suppression apparatus that suppresses an interference signal included in a received signal in the first frequency band by subtracting, and includes a radio in the first frequency band that includes the desired signal and a plurality of interference signals that interfere with the desired signal. When receiving a signal, a radio signal of the second frequency band is input from a radio reception device that receives a radio signal of the second frequency band before being frequency-converted to the interference signal of the first frequency band, Reference signal generating means for generating a reference signal of the first frequency band by frequency-converting the received signal of the second frequency band, and the received signal of the first frequency band are input, and the reference signal and the first frequency band Based on the received signal An interference replica signal generation means for detecting a plurality of interference signals included in the received signal of the first frequency band and generating a plurality of interference replica signals corresponding to at least a part of the detected plurality of interference signals; Interference suppression means for suppressing a plurality of interference signals included in the received signal in the first frequency band by subtracting a plurality of interference replica signals corresponding to the plurality of interference signals from the received signal in the first frequency band; The interference replica signal generation means and the interference so as to continuously execute a plurality of processes including detection of the plurality of interference signals, generation of the plurality of interference replica signals, and suppression of the plurality of interference signals. A plurality of sets of suppression means are provided.
In addition, the interference suppression method according to the present invention provides an interference replica signal corresponding to an interference signal from a received signal in a first frequency band including a desired signal transmitted from a communication terminal and an interference signal that interferes with the desired signal. An interference suppression method for suppressing an interference signal included in a reception signal of the first frequency band by subtracting, wherein the radio signal of the first frequency band includes the desired signal and a plurality of interference signals that interfere with the desired signal. When receiving a signal, receiving a radio signal of the second frequency band before being frequency-converted to an interference signal of the first frequency band; and frequency-converting the received signal of the second frequency band Detecting a plurality of interference signals included in the received signal of the first frequency band based on the step of generating a reference signal of the first frequency band and the received signal of the first frequency band based on the reference signal and the received signal of the first frequency band; Multiple Detecting a plurality of interference signals, comprising: generating a plurality of interference replica signals corresponding to at least a part of the interference signal; and subtracting the plurality of interference replica signals from the received signal of the first frequency band. And the step of generating a plurality of interference replica signals and the step of suppressing the plurality of interference signals are executed a plurality of times in succession.

According to each of the base station, the interference suppression device, and the interference suppression method, when a radio signal in the first frequency band is received, a radio signal in the second frequency band is simultaneously received, and a received signal in the second frequency band is received. Is converted into a first frequency band reference signal, and a plurality of interference signals included in the first frequency band reception signal are respectively generated based on the generated reference signal and the first frequency band reception signal. A plurality of corresponding interference replica signals can be generated. By subtracting the plurality of interference replica signals from the reception signal in the first frequency band, the plurality of interference signals included in the reception signal in the first frequency band can be suppressed.
In addition, according to each of the base station, the interference suppression device, and the interference suppression method, the detection of the plurality of interference signals, generation of the plurality of interference replica signals, and suppression of the plurality of interference signals are executed a plurality of times in succession. In this way, instead of generating multiple interference replica signals corresponding to multiple interference signals included in the received signal and using them for suppression of interference signals, an interference replica signal is generated for each interference signal. Thus, it can be used for suppression of interference signals. As a result, when a plurality of interference signals are included in the received signal in the first frequency band, the influence of other interference signals when generating the interference replica signal corresponding to the interference signal is suppressed, and the interference replica signal is accurately detected. Can be generated. Accordingly, it is possible to reliably suppress a plurality of interference signals generated by frequency conversion from a radio signal having a frequency band different from that of the radio signal received from the communication terminal.

The base station may include two sets of the interference replica signal generation means and the interference suppression means. In this base station, the configuration can be simplified and the processing speed can be increased.
Further, in the base station, the detection of the plurality of interference signals, generation of the plurality of interference replica signals, and suppression of the plurality of interference signals are successively performed a plurality of times in order of increasing strength of the plurality of interference signals. May be. In this base station, an interference replica signal is generated preferentially for an interference signal having a large intensity and a large influence of interference, and is used to suppress the interference signal, and the received signal obtained by subtracting the interference replica signal is used to reduce the intensity. An interference replica signal corresponding to the interference signal is generated and used to suppress the interference signal. Therefore, an interference replica signal can be generated with high accuracy even for an interference signal having a small intensity, and the interference signal can be reliably suppressed.

Further, in the base station, the interference replica signal generation means calculates a value of each of a plurality of parameters necessary for generating the interference replica signal that can be calculated from the reference signal and the received signal of the first frequency band, The interference replica signal may be generated based on the calculated values of the plurality of parameters. In this base station, by using a plurality of parameters necessary for generating an interference replica signal that can be calculated from the reference signal and the received signal in the first frequency band, an interference replica signal generation process necessary for suppressing the interference signal is used. Becomes simple.
In the base station, the parameters used for generating the interference replica signal may be a frequency offset, a delay time, and an amplitude of the interference signal. In this base station, the interference replica signal can be accurately generated by using the frequency offset, delay time, and amplitude of the interference signal to generate the interference replica signal, so that the interference signal suppression processing at a predetermined timing can be performed. Accuracy and efficiency can be improved.
Further, in the base station, the interference replica signal generating means sets a correlation between the reference signal and the received signal in the first frequency band while setting a plurality of sets of frequency offset, delay time and amplitude for the reference signal. By calculating a value and comparing a correlation value calculated for each of a plurality of combinations of the frequency offset, delay time, and amplitude with a preset threshold value, the frequency offset, delay time, and amplitude of the interference signal are estimated. Also good. In this base station, by calculating a correlation value between the reference signal and the received signal in the first frequency band while setting a plurality of sets of frequency offset, delay time and amplitude for the reference signal, the frequency offset of the interference signal, The delay time and amplitude can be estimated with high accuracy. Further, since the frequency offset, delay time and amplitude of the interference signal are estimated by comparing the correlation value with a preset threshold value, the influence of noise can be eliminated.
Further, in the base station, the interference replica signal generation means generates the interference replica signal based on an offset reference signal in which the frequency offset and delay time are set in the reference signal and a weight corresponding to the amplitude. The weight difference may be calculated based on the difference between the received signal in the first frequency band and the interference replica signal and the offset reference signal, and the weight may be updated using the difference. . In this base station, it is possible to improve the accuracy of the interference replica signal as the generation of the interference replica signal is repeated while suppressing the processing load when generating the interference replica signal.
The base station further includes storage means for storing the estimated value of the parameter, and the interference replica signal generation means includes the parameter value stored in the storage means and the reference signal of the first frequency band. The interference replica signal may be generated based on In this base station, since the interference signal can be suppressed by reusing the estimated value of the parameter, the interference signal can be suppressed by simpler processing.
The base station may further include an update unit that repeatedly updates the estimated value of the parameter stored in the storage unit at a predetermined timing, and the update timing may be changeable. In this base station, the estimated value of the parameter can be updated according to changes in the communication environment such as the source of the interference signal and the transmission path, so that the accuracy of the interference signal suppression process over time can be improved.
Further, in the base station, the path of the received signal received by the first receiving unit is divided into a first path on which interference signal suppression processing is performed by the interference suppression unit, and interference signal suppression processing by the interference suppression unit. Reception path switching means for switching between the second path that is not performed may be provided. In this base station, when the interference suppression means stops functioning due to a failure or the like, the received signal can be processed without going through the interference suppression means.
In particular, in this base station, the reception path switching means is configured to switch the path of the reception signal from the first path to the second path when the intensity of the reference signal is less than or less than a threshold. You may provide the control means to control. In this base station, when the interference suppression unit does not function normally due to insufficient reference signal strength, the interference suppression unit prevents the accuracy of interference suppression from being reduced, or inappropriate interference suppression processing is performed. Can be prevented in advance.
In the base station, the received signal in the first frequency band may include a plurality of interference signals having at least one of frequency offset, delay time, and amplitude different from each other. In this base station, even when a plurality of interference signals having different frequency offsets, delay times, and amplitudes are included in the received signal of the first frequency band, each interference signal can be reliably suppressed. .
In the base station, the first frequency band radio signal received by the first receiving means is a 1.5 GHz band radio signal transmitted from the communication terminal and received by the second receiving means. The second frequency band radio signal may be an 11 GHz band radio broadcast signal transmitted from a broadcast satellite. This base station suppresses an interference signal of 1.5 GHz band or 1.4 GHz band, which is frequency-converted from an 11 GHz band radio broadcast signal having a frequency band different from that of a 1.5 GHz band radio signal received from a communication terminal. Can do.
In the base station, the interference signal included in the radio signal in the first frequency band received by the first receiving means is a frequency converter for converting a radio broadcast signal into an intermediate frequency signal and an intermediate frequency signal The leaked signal may be leaked from at least one of the amplifying devices for amplifying the signal. In this base station, it is possible to suppress an interference signal caused by a frequency-converted signal leaked from a booster that amplifies an intermediate-frequency signal obtained by frequency-converting a radio broadcast wave reception signal.

  According to the present invention, a plurality of interference replica signals corresponding to a plurality of interference signals included in a reception signal in the first frequency band are generated, and the plurality of interference replica signals are subtracted from the reception signal in the first frequency band. Thus, it is possible to suppress a plurality of interference signals included in the received signal in the first frequency band. Therefore, it is possible to suppress a plurality of interference signals generated by frequency conversion from a radio signal having a frequency band different from that of the radio signal received from the communication terminal. In particular, according to the present invention, even when the number of interference signals is large, an interference replica signal corresponding to each interference signal can be generated with high accuracy, so that each interference signal can be reliably suppressed.

The schematic block diagram which shows an example of the whole structure of the base station which concerns on one Embodiment of this invention. (A) is explanatory drawing which shows typically the frequency spectrum of the received signal x before interference signal BS-IF is suppressed. (B) is explanatory drawing which shows typically the frequency spectrum of the received signal (output signal) z by which interference signal BS-IF was suppressed. The block diagram which shows the example of 1 structure of an interference suppression process part. The block diagram which shows the other structural example of an interference suppression process part. The block diagram which shows an example of the interference suppression process in an interference suppression process part. (A) And (b) is explanatory drawing which illustrates the some BS-IF interference signal whose magnitude | size of an amplitude is more than a threshold value, respectively. The flowchart which shows the procedure of the interference suppression process which concerns on the other example in an interference suppression process part. Explanatory drawing which shows the BS-IF interference signal arranged in order of the magnitude | size of the amplitude in the interference suppression process of FIG. Explanatory drawing which shows the mode of the search of the interference signal in the other example of interference suppression processing in an interference suppression process part. The block diagram which shows the example of another interference suppression process in an interference suppression process part. The block diagram which shows the other example of interference suppression processing in an interference suppression process part. Explanatory drawing which shows the mode of cancellation of the BS-IF interference signal which concerns on a comparative example. Explanatory drawing which shows the mode of cancellation of the BS-IF interference signal by the interference suppression process of this embodiment. The block diagram which shows an example of the 2 step | paragraph interference suppression process in the interference suppression process part of this embodiment. The block diagram which shows the example of the other 2 step | paragraph interference suppression process in the interference suppression process part of this embodiment. The block diagram which shows the example of the other 2 step | paragraph interference suppression process in the interference suppression process part of this embodiment. The schematic block diagram which shows an example of the whole structure of the base station which concerns on other embodiment which can apply this invention. The schematic block diagram which shows an example of the whole structure of the base station which concerns on other embodiment which can apply this invention. The schematic block diagram which shows an example of the whole structure of the base station which concerns on other embodiment which can apply this invention. Explanatory drawing for demonstrating the subject in the conventional base station.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
Embodiment 1
FIG. 1 is a schematic configuration diagram illustrating an example of the overall configuration of a base station according to an embodiment of the present invention. In FIG. 1, a base station 10 according to this embodiment includes a radio signal (1.5 GHz band) in a first frequency band (1.5 GHz band) from a base station apparatus 20 as a main body, an interference suppression apparatus 30, and a mobile device 80 as a communication terminal. A base station antenna 40 as first receiving means for receiving radio waves), and duplexers (DUPlexers) 50 and 51 for sharing the base station antenna 40 for transmission and reception. The interference suppression device 30 receives an interference suppression processing unit 300 (to be described later) serving as interference suppression means, and a radio signal (radio wave) d _RF (t) of a satellite broadcast BS in the second frequency band (11 GHz band) used for interference suppression. BS receiving system 350.

The BS reception system 350 includes a mobile communication signal x _MS that is a desired signal and its IF interference signal (hereinafter referred to as “BS-IF interference signal”) x _BS-IF generated by a plurality of BS receivers. When a radio signal x in the first frequency band (1.5 GHz band) is received, the radio signal is in the second frequency band (11 GHz band) before being converted into an interference signal in the first frequency band. It functions as a second receiving means for receiving a radio signal (radio wave) d _RF (t) of the satellite broadcast BS. Furthermore, the BS reception system 350 also functions as a reference signal generation unit that generates a reference signal d ₀ (t) in the first frequency band by performing frequency conversion on the reception signal d _RF (t) in the second frequency band. As the BS reception system 350, for example, as shown in the figure, a parabolic antenna (hereinafter referred to as “interference suppression BS antenna”) 351 that is an antenna body, and a BS-RF mounted on the interference suppression BS antenna 351. An existing BS receiving system with a receiver 352 can be used. The BS-RF receiver 352 of the BS receiving system 350 frequency-converts the received signal d _RF (t) in the second frequency band (11 GHz band) to generate a signal d ₀ (t in the first frequency band (1.5 GHz band)). LNB (Low Noise Block Converter). The signal d ₀ (t) output from the BS-RF receiver 352 is sent to the interference suppression device 30 via a coaxial cable. Hereinafter, the BS-IF signal d ₀ (t) frequency-converted to the intermediate frequency BS-IF by the BS-RF receiver 352 is referred to as “BS-IF reference signal” or simply “reference signal”.

The received signal x ₀ (t) in the first frequency band received by the base station antenna 40 is sent to the interference suppression device 30 via the duplexer 50 and processed. The received signal z ₀ (t) processed by the interference suppression device 30 is sent to the base station device 20 via the duplexer 51. The base station antenna 40 and duplexers 50 and 51 are also used when transmitting mobile communication radio signals to the mobile device 80, and mobile communication transmission signals output from the base station apparatus 20. Is sent to the detour path 52 via the duplexer 51 and then sent to the base station antenna 40 via the duplexer 50.

The received signal x in the first frequency band (1.5 GHz band) received by the base station antenna 40 is a mobile communication signal that is a desired signal transmitted from the mobile device 80 as illustrated in FIG. x _MS and a plurality of BS-IF interference signals x _BS-IF . Each of the plurality of BS-IF interference signals x _BS-IF is a signal caused by a leaked radio wave having an intermediate frequency of a satellite broadcast receiving system installed in a home, office, various facilities, or the like. The satellite broadcast receiving system includes a parabolic antenna (hereinafter referred to as “BS antenna”) that receives a radio signal of a satellite broadcast BS in the second frequency band (11 GHz band), and a second satellite broadcast BS received by the BS antenna. An LNB that converts the frequency band BS received signal d _RF (t) to an intermediate frequency, and an amplifier (hereinafter referred to as “BS booster”) that is provided near the BS antenna so as to amplify the intermediate frequency signal after frequency conversion. .). The BS booster amplifies a BS-IF signal having the same frequency as the first frequency band. Here, when the radio wave shielding (shielding) of the BS booster is insufficient or there is a connection error between the BS booster and the coaxial cable connector, the BS-IF signal may leak from the BS booster to the space as radio waves. Since the radio waves leaked from each BS booster travel through different transmission paths, they reach the base station antenna 40 as a plurality of radio signals having different delay times and intensities. In addition, when a radio signal (BS-RF signal) received by the BS antenna is converted into an intermediate frequency signal (BS-IF signal), a frequency offset due to the frequency deviation of the local transmitter for conversion to the intermediate frequency is set. Arise. In this way, a radio signal including a plurality of leaked radio waves having different delay times, intensities, and frequencies is received by the base station antenna 40 as a BF-IF interference signal x _BS-IF included in the received signal x in the first frequency band. The

The received signal x in the first frequency band received by the base station antenna 40 is amplified by the duplexer 50 and then input to the interference suppression device 30, and the interference suppression device 30 receives the BS-IF interference signal x _BS-IF. Received signal z (see FIG. 2B) is input to base station apparatus 20.

The interference suppression device 30 is an interference suppression processing unit that performs processing to suppress the BF-IF interference signal x _BS-IF included in the received signal x in the first frequency band (1.5 GHz band) received by the base station antenna 40. 300. The interference suppression processing unit 300 subtracts replicas of a plurality of BF-IF interference signals x _BS-IF (hereinafter referred to as “interference replica signals”) from the reception signal x of the first frequency band to receive the first frequency band. It acts as an interference suppression means for suppressing the BF-IF interference signal _{x BS-IF} included in the signal x. The interference suppression processing unit 300 functions to cancel the interference signal included in the received signal, and is also referred to as an “interference canceller”. In addition, the interference suppression processing unit 300, based on the reference signal d ₀ (t) generated by the BS receiving system 350 and the received signal x ₀ (t) of the first frequency band received by the base station antenna 40, It also functions as an interference replica signal generation means for generating an interference replica signal.

  FIG. 1 shows an example in which an existing BS reception system 350 having a BS antenna 351 for interference suppression and a BS-RF receiver 352 with a built-in LNB is used as the second reception means and the reference signal generation means. However, it is not limited to this configuration. For example, an existing parabolic antenna may be used only for the BS antenna 351 for interference suppression, and separate devices having high frequency stability may be used for the BS-RF receiver and the frequency converter (LNB). . Further, the interference suppression device 30 may be configured to include a BS-RF receiver and a frequency converter (LNB) configured as individual devices having high frequency stability without including an existing parabolic antenna. .

FIG. 3 is a block diagram illustrating a configuration example of the interference suppression processing unit 300. The interference suppression processing unit 300 of FIG. 3 includes a parameter value estimation unit 301, a parameter value storage unit 302, an interference replica signal generation unit 303, and a subtraction processing unit 304.
The parameter value estimation unit 301 receives an input signal x ₀ (t) that is a received signal in the first frequency band (1.5 GHz band or 1.4 GHz band) received by the base station antenna 40 at a predetermined timing, and interference suppression. Based on the reference signal d ₀ (t) of the first frequency band (1.5 GHz band) obtained by frequency-converting the received signal d _RF (t) of the second frequency band (11 GHz band) received by the BS antenna 351. Thus, the value of the parameter used to generate the interference replica signal corresponding to the BF-IF interference signal x _BS-IF included in the received signal x ₀ (t) is estimated. The parameters for this estimation target, for example, the reference signal _d 0 (t) BF-IF interference signal _{x BS-IF} the delay time for, and the like amplitude or frequency offset.
The parameter value storage unit 302 stores the parameter estimation value estimated by the parameter value estimation unit 301 until the next parameter value is estimated and updated so that it can be used for a plurality of subsequent interference suppression processes. Is.
The interference replica signal generation unit 303 receives the received signal x ₀ (t) based on the parameter value stored in the parameter value storage unit 302 and the reference signal d ₀ (t) in the first frequency band (1.5 GHz band). corresponding to BF-IF interference signal _{x BS-IF} contained in t) to generate an interference replica signal y (t).
The subtraction processing unit 304 subtracts the interference replica signal y (t) generated by the interference replica signal generation unit 303 from the input signal x ₀ (t) that is the received signal in the first frequency band (1.5 GHz band). I do. The reception signal in the first frequency band in which the BF-IF interference signal xBS _-IF is suppressed by the subtraction processing of the subtraction processing unit 304 is output to the base station apparatus 20 as the output signal z ₀ (t).

In the interference suppression processing unit 300 in FIG. 3, the parameter estimation value estimated by the parameter value estimation unit 301 is stored in the parameter value storage unit 302, and therefore can be used continuously for a plurality of subsequent interference suppression processing. . Therefore, the number of parameter value estimation processes by the parameter value estimation unit 301 can be minimized, and the signal processing amount of the interference suppression processing unit 300 can be greatly reduced.
By the way, the estimated value of the parameter may not change greatly even with time. For example, when the interference suppression processing unit 300 is restarted, the estimated value of the parameter does not change significantly from before the restart, so that the parameter estimated value stored in the parameter value storage unit 302 or its surrounding values is changed thereafter. You may make it use for an interference suppression process.

FIG. 4 is a block diagram illustrating another configuration example of the interference suppression processing unit 300. Unlike the configuration example of FIG. 3, the interference suppression processing unit 300 of FIG. 4 is configured to update parameters sequentially, and the estimated value of the parameter estimated by the parameter value estimation unit 301 is estimated for the next parameter value. In addition, the parameter value storage unit 302 that stores data until updating is not provided.
The parameter value estimation unit 301 uses an input signal x ₀ (t) that is a received signal in the first frequency band (1.5 GHz band) received by the base station antenna 40 and a BS antenna 351 for interference suppression at a predetermined timing. BF− included in the received signal x based on the reference signal d ₀ (t) in the first frequency band (1.5 GHz band) obtained by frequency-converting the received signal in the second frequency band (11 GHz band). IF interference signal x Estimates the value of a parameter used to generate an interference replica signal corresponding to _BS-IF .
The interference replica signal generation unit 303 receives the received signal x ₀ (t) based on the parameter value estimated by the parameter value estimation unit 301 and the reference signal d ₀ (t) in the first frequency band (1.5 GHz band). generating a BF-IF interference signal _{x BS-IF} interference replica signal corresponding to y (t) included in).
The subtraction processing unit 304 subtracts the interference replica signal y (t) generated by the interference replica signal generation unit 303 from the input signal x ₀ (t) that is the received signal in the first frequency band (1.5 GHz band). I do. The reception signal in the first frequency band in which the BF-IF interference signal xBS _-IF is suppressed by the subtraction processing of the subtraction processing unit 304 is output to the base station apparatus 20 as the output signal z ₀ (t).

In the interference suppression processing unit 300 in FIG. 4, the parameter estimation value estimated by the parameter value estimation unit 301 is not stored in the parameter value storage unit, but interference with the mobile communication signal x itself used for the parameter value estimation is stored. Since it can be used for suppression processing, the accuracy of interference suppression increases. Also, the time zone during which the mobile communication signal x ₀ (t) is received, the BS booster 91 such as a home that is the source of the interference signal, and the BF-IF interference signal x between the BS booster 91 and the base station 10 _When the transmission characteristics of the _BS-IF change, it is possible to respond quickly to the change.

In the interference suppression processing unit 300 according to the present embodiment, continuously generating the interference replica signals to a plurality of BF-IF interference signal x _BS-IF and the suppression of the interference signal using the interference replica signal twice A two-stage interference suppression processing method is employed.
First, a basic interference suppression processing example used in the two-stage interference suppression processing method in the interference suppression processing unit 300 according to the present embodiment will be described.
[Interference suppression processing example 1]
FIG. 5 is a block diagram illustrating an example of interference suppression processing in the interference suppression processing unit 300. In this interference suppression processing example 1, the mobile communication signal including the BS-IF interference signal is frequency-converted (down-converted) from the first frequency band (1.5 GHz band) to a predetermined frequency band (baseband), and the conversion is performed. An interference replica signal that is a replica of the BS-IF interference signal is generated in a later frequency band, and the interference replica signal generated from the received mobile communication signal that has been compensated for the delay time for generating the interference replica by the processing delay is After subtraction, the frequency is converted (up-converted) to the original first frequency (1.5 GHz band) and output.

In order to generate the interference replica signal, it is necessary to estimate a complex amplitude that is an amplitude including a frequency offset f _offset , a delay time τ, and a phase of each of a plurality of BS-IF interference signals included in the received signal. In particular, the value of the frequency offset f _offset of the BS-IF interference signal varies greatly for each BS booster (BS receiver) that is the source of the BS-IF interference signal. Therefore, highly accurate estimation of the value of the frequency offset f _offset and its correction are very important.

Therefore, in the interference suppression process of FIG. 5, first, the frequency offset f _offset , delay time τ, and complex amplitude of the BS-IF interference signal are estimated. Now, a received signal including the mobile communication signal received by the base station 10 and the BS-IF interference signal is set as x ₀ (t) as a function of time t. The received signal x ₀ (t) is frequency-converted to a predetermined frequency by a down converter (DC) 311 and then sampled at a time interval ΔT by an analog-digital converter (ADC) 312 to receive a received signal x (i) comprising a digital signal. ). Here, i is a natural number representing the sampling order. The sampling time interval ΔT is generally sufficient if a time of about 1/2 or 1/4 of the symbol length (= 1 / radio transmission bandwidth) of the radio signal is sufficient.

On the other hand, in the first frequency band (1.5 GHz band) obtained by frequency-converting the BS received signal d _RF (t) in the second frequency band (11 GHz band) received by the BS antenna 351 for interference suppression provided in the base station 10. The BS-IF signal is set as a reference signal d ₀ (t) as a function of time t. The reference signal d ₀ (t) is frequency-converted to a predetermined frequency by the down converter (DC) 313 and then sampled by the analog-to-digital converter (ADC) 314 at a time interval ΔT to be a digital reference signal d (i ). Here, i is a natural number representing the sampling order.

The estimation processing unit 315 detects a BS-IF interference signal that is frequency offset based on the reference signal d (i). For this purpose, first, a reference signal that is frequency offset by a value obtained by discretizing the frequency offset amount f _offset with respect to the received reference signal d (i) at a frequency interval Δf is denoted as d _off (i, m). _off (i, m) can be expressed by the following equation (1). Here, “j” in equation (1) represents an imaginary number (√−1), and “m” is a natural number representing the order of frequency offsets discretized by Δf. “MΔf” is a discretized frequency offset amount.

Next, the estimation processing unit 315 detects the BS-IF interference signal by obtaining a correlation between the frequency-offset reference signal d _off (i, m) and the received signal x ₀ (i). Now, a reference signal shifted by n is set as d _off (i−n, m). If the correlation calculation value between the received signal x ₀ (i) and the reference signal d _off (i−n, m) is r (n, m), r (n, m) can be expressed by the following equation (2) ( (See FIG. 6). Here, “ ^* ” in equation (2) represents a complex conjugate, and “N _s ” is the number of data used for correlation calculation.

Now, assuming that the range of n is N _{min to} N _max and the range of m is M _{min to} M _max , the estimation processing unit 315 has (N _max −N _min +1) × (M _max −M _min +1) ways. Correlation calculation is performed. Then, the estimation processing unit 315, the calculated correlation value r (n, m) the magnitude of | r (n, m) | is compared with a threshold value _{L th} that predetermines, as shown in the following equation (3) R (n, m) that is equal to or greater than the threshold Lth is _{defined as} the complex amplitude of the BS-IF interference signal.

Now, let K _max be the number of BS-IF interference signals that are equal to or greater than the threshold value L _th , arrange the BS-IF interference signals in order from the largest, and BS-IF interference that has the kth magnitude. Let r (n _k , m _k ) be the complex amplitude of the signal. In this case, r (n _k , m _k ) is the complex amplitude of the kth BS-IF interference signal and has the following three elements.
Delay time τ: _nk ΔT
Frequency offset f _offset : m _k Δf
Amplitude: r (n _k , m _k )

FIGS. 6A and 6B are explanatory diagrams illustrating a plurality of BS-IF interference signals each having an amplitude greater than or _equal to a threshold value Lth. In FIG. 6, in the coordinate space of the frequency offset and the delay time, the amplitudes are r (n ₁ , m ₁ ), r (n ₂ , m ₁ ), r (n ₃ , m ₂ ), r (n ₄ , m ₂ ), R (n ₄ , m ₃ ), r (n ₅ , m ₃ ), and six BS-IF interference signals having amplitudes greater than or equal to the threshold L _th are illustrated.

If the k-th BS-IF interference signal generated by the interference replica signal generation units 316 and 317 is y _{nk, mk} (i), y _{nk, mk} (i) is the next using the reference signal d (i). It is represented by Formula (4). This BS-IF interference signal y _{nk, mk} (i) is an interference replica signal corresponding to the BS-IF interference signal included in the received signal x (i).

However, the equation h (n _k , m _k ) in the equation (4) is expressed by the following equation (5) using the complex amplitude r (n _k , m _k ).

Next, the addition processing unit 318 adds all BS-IF interference signals (interference replica signals) y _{nk, mk} (i) from 1 to Kmax. In the subtraction processing unit 320, all BS-IF interference signals (interference replica signals) y _{nk, mk} (i) added by the addition processing unit 318 are received signals x (i) subjected to delay processing by the processing delay unit 319. By subtracting from, it is possible to obtain an output signal z (i) composed of a digital signal output to the base station apparatus 20. This output signal z (i) is expressed by the following equation (6).

The output signal z (i) output from the subtraction processing unit 320 is converted into an analog signal by the digital analog converter (DAC) 321 and then the first frequency band (1.5 GHz band) by the up converter (UC) 322. By performing frequency conversion to a predetermined frequency, an output signal z ₀ (t) output to the base station device 20 is obtained.

[Interference suppression processing example 2]
FIG. 7 is a flowchart illustrating a procedure of another interference suppression processing example in the interference suppression processing unit 300. In this interference suppression processing example 2, from the plurality of BS-IF interference signals detected by the correlation calculation processing in the estimation processing unit 315, the amplitude magnitude | r (n _k , m _k) | selects the BS-IF interference signal is the threshold value _{L th} or more (step 101). Here, when the number Kmax of BS-IF interference signals whose amplitude | r (n _k , m _k ) | is equal to or greater than a threshold value is large, the signal processing capability causes the selected BS-IF interference signal to There are cases where interference suppression processing cannot be executed for all. Therefore, in this interference suppression processing example 2, as shown in FIG. 8, the amplitude magnitudes of a plurality of BS-IF interference signals selected to satisfy | r (n _k , m _k ) | ≧ L _th | r (n _k , m _k ) | are arranged in descending order (step 102), and BS-IF interference signals corresponding to the required number K _need (≦ Kmax) in the descending order of | r (n _k , m _k ) | Further selection is made (step 103). Thus the BS-IF interference signal of the selected required number K _need only generate an interference replica signal to perform interference suppression processing (step 104).
In this interference suppression processing example 2, the BS-IF interference signals detected based on the result of the correlation calculation processing are arranged in order of magnitude of the amplitude, and the interference suppression processing is executed only for the required number of BS-IF interference signals in descending order. By doing so, it becomes possible to cancel the optimum BS-IF interference signal in consideration of the signal processing capability, and the BS-IF interference signal cancellation can be made more efficient.
Since the other processing of the interference suppression processing example 2 is the same as that of the interference suppression processing example 1, description thereof is omitted.

[Interference suppression processing example 3]
This interference suppression processing example 3 is intended to speed up the search for the BS-IF interference signal in the interference suppression processing in the interference suppression processing unit 300. Note that the description of the same processing as in the interference suppression processing example 1 described above in the interference suppression processing example 3 is omitted.

In this interference suppression processing example 3, _{assuming that} the maximum range of the frequency offset amount f _offset is f _wide , N _max = f _wide / Δf is the number of searches when performing a search by discretization at a frequency interval Δf. If the maximum range of the delay time is T _wide , M _max = T _wide / ΔT is the number of searches when discretized at a time interval ΔT. Therefore, N _max × M _max is the total number of searches.

Further, the processing time of the correlation calculations per time is proportional to the number of data N _s to be used for the calculation. Therefore, it is necessary to calculate N _max × M _max × N _s . As N _max , M _max , and N _s are increased, the detection accuracy of the BS-IF interference signal is improved. However, the processing time increases and the processing delay increases accordingly. As a result, the detection of the BS-IF interference signal is delayed.

Accordingly, the present interference suppression processing example 3, first, then the frequency interval as shown Delta] f, the time interval [Delta] T, a plurality sets of data number N _s of the correlation calculation. And those values are adaptively changed.
Frequency interval: Δf = Δf ₁ , Δf ₂ , ---. However, (Δf ₁ > Δf ₂ > −−−−)
Time interval: ΔT = ΔT ₁ , ΔT ₂ , ---. However, (ΔT ₁ > Δf ₂ > −−−−)
Number of data for correlation calculation: N _s = N _s1 , N _s2 , ---. However, (N _s1 <N _s2 <----)

Here, it sets larger frequency interval Delta] f, and the time interval [Delta] T, is set to be smaller the number of data N _s of the correlation calculation. Specifically, the frequency interval is set to Δf ₁ , the time interval ΔT ₁ , the number of correlation calculation data is set to N _s1 , the correlation value is calculated, the amplitude is compared with the threshold value L _th, and the following equation (7 ) when a and (8) are shown as the threshold _{L th} or more, the _n 1, _m is provisionally determined that there is a BS-IF interference signal to a value of _1, the frequency offset value _{n 1} Delta] f at that time _1. Record the delay time m ₁ ΔT ₁ .

Next, FIG. 9 and the following equation (9), as shown in (10), recorded frequency offset value _{n 1} Delta] f _1, the periphery of the delay time _{m 1 ΔT 1 Δf 1} is smaller than the frequency interval Delta] f _2, [Delta] T ₁ Correlation values are calculated with a smaller time interval ΔT ₂ and with a correlation calculation data number N _s2 greater than N _s1 .

However, n ₂ and m ₂ in the above formulas (9) and (10) are limited to the vicinity of the frequency offset value n ₁ Δf ₁ and delay time m ₁ ΔT ₁ recorded as shown in the following formula (11). To do.

Here, Δf _w and ΔT _w correspond to a frequency offset width and a delay time width for limiting the search range, respectively. By limiting the search range in this way, the processing time can be shortened. Further, by searching with a smaller frequency interval Δf ₂ and a smaller time interval ΔT ₂ , it is possible to estimate a highly accurate frequency offset value and delay time, and to increase the number of correlation calculation data N _s2 . A high amplitude r (n _k , m _k ) can be estimated. As a result, the BS-IF interference signal cancellation effect can be increased.

As described above, in this interference suppression processing example 3, it is possible to search for a high-accuracy BS-IF interference signal at high speed and to reduce the amount of processing. In the description of the interference suppression processing example 3, the two search range limiting methods are shown. However, by limiting the search range in the same manner as the three or four methods, the processing time can be further shortened and the accuracy can be improved. High r (n _k , m _k ) can be estimated.

[Interference suppression processing example 4]
FIG. 10 is a block diagram showing still another example of interference suppression processing in the interference suppression processing unit 300. Note that a description of the same processing as in the above-described interference suppression processing example 1 (see FIG. 5) will be omitted.
In the above-described interference suppression processing example 1, the received signal x ₀ (t) including the BS-IF interference signal received by the base station 10 is frequency-converted (down-converted) and processed in a low frequency band. Specifically, after canceling the BS-IF interference signal in a low frequency band, the frequency is converted (up-converted) to the original mobile communication frequency band (first frequency band: 1.5 GHz band) and output. Yes.

In the interference suppression processing example 4, the received signal x0 (t) including the BS-IF interference signal is amplified by the amplifier 323 without frequency conversion, and the interference replica signal y (i) which is a replica of the BS-IF interference signal is reduced in frequency. It is generated with a belt. Then, the interference replica signal y (i) is frequency-converted (up-converted) to generate an interference replica signal y (t), and the up-converted interference replica signal y (t) is used to change the frequency of mobile communication. The BS-IF interference signal is canceled in the band (first frequency band: 1.5 GHz band). According to the fourth interference suppression processing example 4, for example, even if the estimation processing unit 315 and the interference replica signal generation unit do not function due to a failure or the like, the received signal x ₀ (t) received by the base station antenna 40 is used as the base station device 20. Can be output.

[Interference suppression processing example 5]
FIG. 11 is a block diagram illustrating still another example of interference suppression processing in the interference suppression processing unit 300. Note that a description of the same processing as in the above-described interference suppression processing example 1 (see FIG. 5) will be omitted.
In the fifth embodiment, the BS reception signal d _RF (t) in the second frequency band (11 GHz band) is received by the interference suppression BS antenna 351 installed in the base station 10 as in the above-described interference suppression processing example 1, Is converted to the same frequency as the BS-IF interference signal to generate the reference signal d ₀ (t). Based on this reference signal d ₀ (t), an interference replica signal y (t) that is a replica of a plurality of BS-IF interference signals received by the base station 10 is created, and the interference replica signal y (t) is received signal. The BS-IF interference signal is canceled by adding x ₀ (t) in reverse phase.

  In particular, in this interference suppression processing example 5, the weight calculation unit (estimation processing unit) 324 sequentially calculates the weight w for creating the interference replica signal y (t) as described below. The weight used here is a weighting coefficient to be applied to the reference signal when generating the interference replica signal y (t), and corresponds to the complex amplitude h in the interference suppression processing example 1.

First, the weight calculation unit 324 needs to detect a BS-IF interference signal having a frequency offset based on the reference signal d (i). For this purpose, first, a reference signal that is frequency offset by a value obtained by discretizing the frequency offset amount f _offset with respect to the received reference signal d (i) at a frequency interval Δf is denoted as d _off (i, m). _off (i, m) can be expressed by the following equation (12). Here, “j” in Equation (12) represents an imaginary number (√−1), and “m” is a natural number representing the order of frequency offsets discretized by Δf. “MΔf” is a discretized frequency offset amount. The sampling time interval ΔT is generally sufficient if a time of about 1/2 or 1/4 of the symbol length (= 1 / radio transmission bandwidth) of the radio signal is sufficient.

First, a method for generating weights for creating an interference replica signal will be described. Now, assuming that the weight for creating the interference replica signal is w (n, m), the interference replica signal y (i), which is a replica of the BS-IF interference signal, has the weight w (n, m) and the reference signal d. It is given by the following equation (13) using _off (i, m). Note that n and m are the same variables as in equation (2).

Next, the update of the weight w (n, m) will be described. A weight difference Δw (n, m) is calculated by performing the calculation shown in the following equation (14) on the signal obtained by subtracting the interference replica signal y (i) from the received signal x (i). In Expression (14), “ ^* ” represents a complex conjugate, and “N _s ” represents the number of data used for calculating the weight difference Δw.

The weight w (n, m) obtained by correcting the difference Δw (n, m) with respect to the current weight w (n, m) is given by the following equation (15).

By the way, in interference suppression processing example 5, first, the presence or absence of a BS-IF interference signal is determined. Here, determination of the presence / absence of a BS-IF interference signal will be described.
As an example, the initial value of the weight is given by the following equation (16).

When the weight difference Δw (n, m) is calculated, the weight difference Δw (n, m) is expressed by the following equation (17).

Therefore, the next weight w (n, m) is represented by the following equation (18) because the initial weight is w (n, m) = 0.

The weight calculation unit 324 detects a BS-IF interference signal that is frequency-offset based on the reference signal d (i) based on the weight of Expression (18).
Similarly to the above-described interference suppression processing example 1, when the range of n is N _{min to} N _max and the range of m is M _{min to} M _max , the weight calculation unit 324 has (N _max −N _min +1) × ( M _max -M _min +1) correlation calculations are performed. The magnitude of the calculated weights w (n, m) | w (n, m) | is compared with a threshold value _{L th} have preset the threshold _{L th} or more is w (n, m) the BS-IF Simultaneously with the complex amplitude of the interference signal, it is determined that there is a BS-IF interference signal at the position (nΔT, mΔf).
If the same control as in the above-described interference suppression processing example 3 is performed, the optimum BS-IF interference signal can be canceled in consideration of the signal processing capability, and the BS-IF interference signal cancellation efficiency is improved. be able to.
Incidentally, the number of BS-IF interference signal becomes the threshold value _{L th} or more and _{K max.} Let w (n _k , m _k ) be the weight of the k-th BS-IF interference signal arranged in order. The kth BS-IF interference signal has the following elements.
Delay time τ: _nk ΔT
Frequency offset f _offset : m _k Δf
Weight (equivalent to amplitude): w (n _k , m _k )

Then, an interference replica signal y (i) that is a replica of the BS-IF interference signal is sequentially generated as shown in the following equation (19) with respect to K _max BS-IF interference signals determined to have interference. , Subtract from the received signal x (i).

The output signal z (i) is expressed by the following equation (20).

Similarly to the above-described interference suppression processing example 2, | w (n _k , m _k ) | is arranged in descending order, and the required number K _need (≦ Kmax) in descending order of | w (n _k , m _k ) | amount corresponding select BS-IF interference signal, it executes the generated and interference suppression processing an interference replica signal only BS-IF interference signal required number K _need chosen. Thereby, the amount of signal processing can be reduced without significantly reducing the interference suppression processing.

Next, the two-stage interference suppression process in the interference suppression processing unit 300 according to the embodiment of the present invention will be described.
In the estimation of the frequency offset and the delay time offset in the estimation processing unit 315, there is a method in which a plurality of BS-IF interference signals are detected in a lump and an interference replica is created. However, in this method, when the number of BS-IF interference signals is large, when one BS-IF interference signal is detected, the remaining other BS-IF interference signals become interference sources, and BS-IF interference The detection accuracy may be deteriorated.

Now, the BS-IF interference signal sampled at the time interval ΔT received by the base station 10 is b (iΔT), the mobile communication signal (cell phone signal) which is the desired signal is w (iΔT), and the received signal obtained by adding them together Is x (i), the received signal x (i) is expressed by the following equation (21). N ₀ (i) in the equation is receiver noise.

Here, when the correlation r (n _k , m _k ) for calculating the amplitude of the k-th BS-IF interference signal is calculated, the following equation (22) is obtained.

Here, n _w is the residual noise after the correlation calculation of the mobile communication signal, n _{h, j} is the residual noise after the correlation calculation of the j-th BS-IF interference signal, n _n is the post-correlation calculation of the receiver noise Residual noise. As shown in the above equation (13), when the number of BS-IF interference signals is large, the residual noise of the BS-IF interference signals increases, and the estimation accuracy of the BS-IF interference signals decreases. In particular, as illustrated in FIG. 12, the signal-to-noise ratio value (SINR ₂ ) of BS-IF interference signals (P 2 and P 3 in the figure) having a low strength (reception power P) among a plurality of BS-IF interference signals. , SINR ₃ ) becomes small due to the influence of the BS-IF interference signal (P1 in the figure) whose strength (reception power P) is large, and the estimation accuracy of the BS-IF interference signal tends to be lowered.

  Therefore, in this embodiment, in order to improve the estimation accuracy of the BS-IF interference signal, instead of collectively detecting the BS-IF interference signal, interference is performed in descending order of the BS-IF interference signal as shown in FIG. The BS-IF interference signal is sequentially estimated by canceling and sequentially estimating the next largest BS-IF interference signal from the canceled signal. Thus, by sequentially canceling the BS-IF interference signal in the order of increasing strength (power), the signal-to-noise ratio (SINR) at the time of detecting the BS-IF interference signal can be improved. Thereby, since the detection accuracy of the BS-IF interference signal is greatly improved, the estimation accuracy of the BS-IF interference signal can be improved.

  FIG. 14 is a block diagram illustrating an example of a two-stage interference suppression process in the interference suppression processing unit 315 of the present embodiment. The example of FIG. 14 is an example in which two stages of the interference suppression processing blocks shown in FIG. 5 are provided. The basic processing contents (detection of a BS-IF interference signal, generation of an interference replica signal, and cancellation processing of a BS-IF interference signal using the interference replica signal) in each of the interference suppression processing blocks 300A and 300B are as follows: Since this is the same as the process in FIG. 5 described above, the description thereof is omitted.

The interference suppression processing unit 315 in FIG. 14 detects a plurality of BS-IF interference signals whose intensity is greater than or equal to a threshold value included in the received signal x ₀ (t) in the first frequency band received by the base station antenna 40, Each of the interference suppression processing blocks 300A and 300B sequentially performs processing for each predetermined number of BS-IF interference signals in order of increasing strength (power or amplitude) of a plurality of detected BS-IF interference signals. For example, when the maximum cancellation number of BS-IF interference signals per interference suppression processing block 300A, 300B is q (for example, 10 to 20), processing is performed as follows.

First, in the first-stage interference suppression processing block 300A, a plurality of BS-IF interference signals included in the received signal x ₀ (t) in the first frequency band are detected. Then, for q BS-IF interference signals having a high intensity among the detected BS-IF interference signals, generation of an interference replica signal and cancellation processing of the BS-IF interference signal using the interference replica signal And the received signal z _q (i) after the cancellation process is output.
Next, in the second-stage interference suppression processing block 300B, a plurality of BS-IF interference signals included in the reception signal zq (i) after the cancellation processing are detected. Then, for q BS-IF interference signals having a high intensity among the detected BS-IF interference signals, generation of an interference replica signal and cancellation processing of the BS-IF interference signal using the interference replica signal To output the output signal z (i) after the cancel processing.
Next, the output signal z (i) output from the second-stage interference suppression processing block 300B is converted into an analog signal by the digital-analog converter (DAC) 321 and then the first frequency is output by the up-converter (UC) 322. By performing frequency conversion to a predetermined frequency in a band (1.5 GHz band), an output signal z ₀ (t) output to the base station apparatus 20 is obtained.
Through the above-described two-stage interference suppression process, an interference replica signal is simultaneously generated for every q (q ≠ 1) for a total of 2q BS-IF interference signals, and q BS BSs are generated using the interference replica signals. -Can be canceled for each IF interference signal. Accordingly, when the number of the plurality of BS-IF interference signals included in the received signal x ₀ (t) in the first frequency band is large, compared to the case where the generation and cancellation processing of the interference replica signal are collectively performed for the near. Thus, since an interference replica signal corresponding to each BS-IF interference signal can be generated with high accuracy, each BS-IF interference signal can be reliably suppressed. This is particularly effective when the number of BS-IF interference signals included in the received signal x ₀ (t) in the first frequency band is large (for example, in the case of several tens or more BS-IF interference signals).

  FIG. 15 is a block diagram illustrating a two-stage interference suppression process according to another example in the interference suppression processing unit 315 of the present embodiment. The example of FIG. 15 is an example in which the interference suppression processing block shown in FIG. 10 is provided in two stages. The basic processing contents (detection of a BS-IF interference signal, generation of an interference replica signal, and cancellation processing of a BS-IF interference signal using the interference replica signal) in each of the interference suppression processing blocks 300A and 300B are as follows: Since this is the same as the processing in FIG.

The interference suppression processing unit 315 in FIG. 15 detects a plurality of BS-IF interference signals whose intensity is greater than or equal to a threshold included in the received signal x ₀ (t) in the first frequency band received by the base station antenna 40, Each of the interference suppression processing blocks 300A and 300B sequentially performs processing for each predetermined number of BS-IF interference signals in order of increasing strength (power or amplitude) of a plurality of detected BS-IF interference signals. For example, when the maximum cancellation number of BS-IF interference signals per interference suppression processing block 300A, 300B is q (for example, 10 to 20), processing is performed as follows.

Unlike the case of FIG. 14, the interference suppression processing unit 315 of FIG. 15 performs frequency conversion by the down converter (DC) 311, AD conversion by the analog digital converter (ADC) 312, and digital for each of the interference suppression processing blocks 300 </ b> A and 300 </ b> B. DA conversion by an analog converter (DAC) 321 and frequency conversion by an up converter (UC) 322 are performed.
First, in the first-stage interference suppression processing block 300A, the analog first received signal x ₀ (t) in the first frequency band is converted into a digital received signal x ₀ (i), and then the received signal x ₀ (i). A plurality of BS-IF interference signals included in the. Then, for q BS-IF interference signals having a high intensity among the detected BS-IF interference signals, generation of an interference replica signal and cancellation processing of the BS-IF interference signal using the interference replica signal Is executed, and the analog reception signal z _q (t) after cancellation processing that has been frequency-converted to a predetermined frequency in the first frequency band (1.5 GHz band) is output.
Next, in the second-stage interference suppression processing block 300B, after the received signal zq (t) after the cancellation process is converted into a digital received signal zq (i), a plurality of signals included in the received signal zq (i) are included. The BS-IF interference signal is detected. Then, for q BS-IF interference signals having a high intensity among the detected BS-IF interference signals, generation of an interference replica signal and cancellation processing of the BS-IF interference signal using the interference replica signal Is executed, and the output signal z (t) after the cancellation processing that has been frequency-converted to a predetermined frequency in the first frequency band (1.5 GHz band) is output.
By the above-described two-stage interference suppression processing, as in the case of FIG. 14, interference replica signals are simultaneously generated for every q (q ≠ 1) for a total of 2q BS-IF interference signals. It is possible to cancel every q BS-IF interference signals using the signal. Accordingly, when the number of the plurality of BS-IF interference signals included in the received signal x ₀ (t) in the first frequency band is large, compared to the case where the generation and cancellation processing of the interference replica signal are collectively performed for the near. Thus, since an interference replica signal corresponding to each BS-IF interference signal can be generated with high accuracy, each BS-IF interference signal can be reliably suppressed. This is particularly effective when the number of BS-IF interference signals included in the received signal x ₀ (t) in the first frequency band is large (for example, in the case of several tens or more BS-IF interference signals).

  FIG. 16 is a block diagram illustrating an example of a two-stage interference suppression process according to still another example in the interference suppression processing unit 315 of the present embodiment. The example of FIG. 16 is an example in which two stages of interference suppression processing blocks shown in FIG. 11 are provided. The basic processing contents (detection of a BS-IF interference signal, generation of an interference replica signal, and cancellation processing of a BS-IF interference signal using the interference replica signal) in each of the interference suppression processing blocks 300A and 300B are as follows: Since it is the same as the process in FIG.

In the interference suppression processing unit 315 in FIG. 16, a plurality of BS-IF interference signals whose intensity is greater than or equal to a threshold included in the received signal x ₀ (t) in the first frequency band received by the base station antenna 40 are detected, Each of the interference suppression processing blocks 300A and 300B sequentially performs processing for each predetermined number of BS-IF interference signals in order of increasing strength (power or amplitude) of a plurality of detected BS-IF interference signals. For example, when the maximum cancellation number of BS-IF interference signals per interference suppression processing block 300A, 300B is q (for example, 10 to 20), processing is performed as follows.

Unlike the case of FIG. 14, the interference suppression processing unit 315 of FIG. 16 creates an interference replica signal y (t) using the weight w as shown in FIG.
First, in the first-stage interference suppression processing block 300A, a plurality of BS-IF interference signals included in the received signal x ₀ (t) in the first frequency band are detected. Then, for q BS-IF interference signals having high intensity among the detected plurality of BS-IF interference signals, generation of an interference replica signal using the weight w and BS-IF using the interference replica signal The interference signal cancel process is executed, and the received signal z _q (i) after the cancel process is output.
Next, in the second-stage interference suppression processing block 300B, a plurality of BS-IF interference signals included in the reception signal zq (i) after the cancellation processing are detected. Then, for q BS-IF interference signals having high intensity among the detected plurality of BS-IF interference signals, generation of an interference replica signal using the weight w and BS-IF using the interference replica signal The cancel process of the interference signal is executed, and the output signal z (i) after the cancel process is output.
Next, the output signal z (i) output from the second-stage interference suppression processing block 300B is converted into an analog signal by the digital-analog converter (DAC) 321 and then the first frequency is output by the up-converter (UC) 322. By performing frequency conversion to a predetermined frequency in a band (1.5 GHz band), an output signal z ₀ (t) output to the base station apparatus 20 is obtained.
By the above-described two-stage interference suppression processing, as in the case of FIG. 14, interference replica signals are simultaneously generated for every q (q ≠ 1) for a total of 2q BS-IF interference signals. It is possible to cancel every q BS-IF interference signals using the signal. Therefore, when the number of a plurality of BS-IF interference signals included in the received signal x ₀ (t) in the first frequency band is large, each BS is more likely to generate and cancel the interference replica signal than when performing a batch processing. Since the interference replica signal corresponding to the IF interference signal can be generated with high accuracy, each BS-IF interference signal can be reliably suppressed. This is particularly effective when the number of BS-IF interference signals included in the received signal x ₀ (t) in the first frequency band is large (for example, in the case of several tens or more BS-IF interference signals).

  In the examples of FIGS. 14 to 16 described above, the case where the interference suppression processing block has two stages has been described. However, the present invention can also be applied to the case where the interference suppression processing block has three or more stages.

[Embodiment 2]
FIG. 17 is a schematic configuration diagram illustrating an example of the overall configuration of a base station according to another embodiment to which the present invention is applicable. Note that, in the configuration of the base station according to the present embodiment, the same parts as those shown in FIGS.

The base station 10 according to the present embodiment is a configuration example in the case where diversity reception is performed using two base station antennas 40 (# 1) and 40 (# 2). In FIG. 17, the signals received by the base station antennas 40 (# 1) and 40 (# 2) are x ₀ (t) and x ₀ ′ (t), respectively. In addition, the first interference suppression processing unit (BS-IF interference canceller) 300 (# 1) and the second interference suppression processing unit (BS-IF interference canceller) 300 (# 2) constituting the interference suppression device 30 are completely different. It is the same configuration. Also, the BS broadcast RF signal d _RF (t) received by the interference suppression BS antenna 351 installed in the base station 10 is frequency-converted to the same frequency as the BS-IF interference signal to generate the reference signal d ₀ (t). doing. Then, the generated reference signal d ₀ (t) is branched into two, the first interference suppression processing unit 300 (# 1) and the second one provided for each of the base station antennas 40 (# 1) and 40 (# 2). Each is input to the interference suppression processing unit 300 (# 2).

  In addition, the interference suppression process in each of the first interference suppression processing unit 300 (# 1) and the second interference suppression processing unit 300 (# 2) in FIG. 17 is any of the interference suppression processing examples 1 to 5 described above. Interference suppression processing may be used. Further, when communication is performed from the base station apparatus 20 to the mobile device, the mobile communication signal is transmitted from the base station antenna 40 (# 1) by switching the signal path by the duplexer (DUP: Duplexer) 50, 51. Can be sent.

[Embodiment 3]
FIG. 13 is a schematic configuration diagram illustrating an example of the overall configuration of a base station according to still another embodiment to which the present invention is applicable. Note that, in the configuration of the base station according to the present embodiment, the same parts as those shown in FIGS.

The base station 10 of the present embodiment is a configuration example in the case where diversity reception is performed by two base station antennas 40 (# 1) and 40 (# 2), as in the embodiment of FIG. In FIG. 18, the signals received by the base station antennas 40 (# 1) and 40 (# 2) are x ₀ (t) and x ₀ ′ (t), respectively. In addition, the first interference suppression processing unit (BS-IF interference canceller) 300 (# 1) and the second interference suppression processing unit (BS-IF interference canceller) 300 (# 2) constituting the interference suppression device 30 are completely different. It is the same configuration. In addition, switches 70 and 71 that directly pass the received signals x ₀ (t) and x ₀ ′ (t) are provided for each of the base station antennas 40 (# 1) and 40 (# 2). The switch 70 uses the path of the received signal x ₀ (t), the first path where the interference signal suppression process is performed by the first interference suppression processing unit 300 (# 1), and the first interference suppression processing unit 300 (# 1). ) Functions as reception path switching means for switching to and from the second path where interference signal suppression processing is not performed. Similarly, the switch 71 uses a path of the reception signal x ₀ ′ (t) as a first path where the interference signal suppression process is performed by the second interference suppression processing unit 300 (# 2), and a second interference suppression process. It functions as a reception path switching means for switching to and from the second path where the interference signal suppression processing by the unit 300 (# 2) is not performed. When the first interference suppression processing unit 300 (# 1) and the second interference suppression processing unit 300 (# 2) do not function due to a failure or the like, the control device 74 as the control unit receives the received signal x ₀ (t), By performing control to switch the switches 70 and 71 so as to directly pass x ₀ ′ (t), the received signals x ₀ (t) and x ₀ ′ (t) are respectively sent to the interference suppression processing units 300 (# 1). ), 300 (# 2) can be output directly to the base station apparatus 20 without going through.

In addition, the control device 74 detects each received signal x ₀ (t) when the intensity of the reference signal d ₀ (t) (for example, the power of the reference signal or SNR: Signal to Noise Ratio) is less than or less than the threshold. ), And the switch 70 and 71 may be controlled so that the route x ₀ ′ (t) is switched from the first route to the second route. When the control causes the first interference suppression processing unit 300 (# 1) and the second interference suppression processing unit 300 (# 2) to stop functioning normally due to insufficient strength of the reference signal d ₀ (t). In addition, it is possible to prevent the accuracy of interference suppression in each interference suppression processing unit 300 (# 1) and 300 (# 2) from being lowered, and to prevent inappropriate interference suppression processing from being performed in advance.

In the present embodiment, when the first interference suppression processing unit 300 (# 1) and the second interference suppression processing unit 300 (# 2) do not function simultaneously due to a failure or the like, the following restoration algorithm is used. It can be recovered. When failures occur in the first interference suppression processing unit 300 (# 1) and the second interference suppression processing unit 300 (# 2) at the same time, the control device 74 receives the received signals x ₀ (t) and x ₀ ′ (t). The switches 70 and 71 are switched so as to pass directly. Thereby, communication to the base station apparatus 20 is securable. Next, the control device 74 tries to recover the function by resetting both the first interference suppression processing unit 300 (# 1) and the second interference suppression processing unit 300 (# 2). Then, by switching one of the switches 70 and 71, the signal from one of the plurality of interference suppression processing units (for example, the first interference suppression processing unit 300 (# 1)) is changed to the base station device 20 side. To monitor the status. This monitoring can be performed in the base station apparatus 20. If the state can be recovered, the switch is kept switched so that the signal from the interference suppression processing unit is output to the base station apparatus 20 side. Next, the other switch is controlled so that a signal from the other of the plurality of interference suppression processing units (for example, the second interference suppression processing unit 300 (# 2)) is output to the base station device 20 side, Monitor status. If the state can be recovered, the switch is kept switched so that the signal from the interference suppression processing unit is output to the base station apparatus 20 side. By this control, it is possible to prevent both of the diversity receptions from being cut off at the same time, and the reliability of the base station can be improved.

  Note that the interference suppression processing in each of the first interference suppression processing unit 300 (# 1) and the second interference suppression processing unit 300 (# 2) in FIG. 18 is any of the interference suppression processing examples 1 to 5 described above. Interference suppression processing may be used. When communication is performed from the base station apparatus 20 to the mobile device, the mobile communication signal can be transmitted from the base station antenna 40 (# 1) by switching the signal path by the duplexers 50 and 51. it can.

  1, FIG. 17, and FIG. 18, the example in which the interference suppression device 30 including the interference suppression processing unit 300 or the like is provided separately from the base station device 20 has been described. Or the like may be incorporated in the base station apparatus 20.

FIG. 19 is a schematic configuration diagram showing an example of the overall configuration of a base station according to still another embodiment to which the present invention can be applied, in which the interference suppression device 30 is incorporated in the base station device 20. Note that, in the configuration of the base station according to the present embodiment, the same parts as those shown in FIG.
In FIG. 19, a base station apparatus 20 provided in the base station 10 includes a receiving apparatus 200 and a transmitting apparatus 210, and the above-described interference suppression apparatus 30 is incorporated. The interference suppression processed reception signal z ₀ (t) output from the interference suppression device 30 is sent to the reception device 200. The mobile communication signal output from the transmission device 210 is sent to the base station antenna 40 via the duplexer 50 and transmitted toward the mobile device.

As described above, according to each of the above embodiments, the interference replica signals corresponding to the plurality of BS-IF interference signals x _BS-IF included in the reception signal x in the first frequency band (1.5 GHz band) are generated, respectively. By subtracting the interference replica signal from the received signal x in the first frequency band, a plurality of BS-IF interference signals x _BS-IF included in the received signal x in the first frequency band can be suppressed. Therefore, a plurality of BS-IFs in the first frequency band (1.5 GHz band) generated by frequency conversion from a radio signal in the second frequency band (11 GHz band) different from the radio signal received from the mobile device 80. The interference signal xBS _-IF can be suppressed.

In each of the above embodiments, the first frequency band is the 1.5 GHz band, the second frequency band is the 11 GHz band for BS broadcasting, and a radio wave that is leaked from the BS booster 91 installed in a home or the like. Although the case where the signal is an interference signal has been described, the present invention is not limited to this. In addition, the present invention can be applied in the same manner as long as the base station 10 can receive the radio signal in the second frequency band before the frequency conversion that is the source of the interference signal in the first frequency band. The effect is obtained.
Further, the estimation and generation of interference replica signals are not limited to the above embodiments. For example, a least mean square (LMS) algorithm, a recursive least square (RLS) algorithm, an ultra-high resolution algorithm such as MUSIC (Multiple Signal Classification), and a two-dimensional LMS algorithm are similarly used. In some cases, similar effects can be obtained.

DESCRIPTION OF SYMBOLS 10 Base station 20 Base station apparatus 30 Interference suppression apparatus 40 Base station antenna 50, 51 Duplexer 70, 71 Switch 74 Control apparatus 80 Mobile device 300 Interference suppression processing part 300A First stage interference suppression processing block 300B Second stage Interference suppression processing block 301 Parameter value estimation unit 302 Parameter value storage unit 303 Interference replica signal generation unit 304 Subtraction processing unit 315 Estimation processing unit 350 BS reception system 351 BS antenna for interference suppression (parabolic antenna)
352 BS-RF receiver

Japanese Patent Laid-Open No. 2001-267942

Claims (16)

A base station capable of wireless communication with a communication terminal,
First receiving means for receiving a radio signal in a first frequency band including a desired signal transmitted from a communication terminal and a plurality of interference signals interfering with the desired signal;
When receiving a radio signal of the first frequency band including the desired signal and the plurality of interference signals, a radio signal of the second frequency band before being frequency-converted to the interference signal of the first frequency band Second receiving means for receiving;
A reference signal generating means for generating a first frequency band reference signal by frequency-converting the received signal in the second frequency band; and the first frequency based on the reference signal and the received signal in the first frequency band. An interference replica signal generating means for detecting a plurality of interference signals included in a band reception signal and generating a plurality of interference replica signals corresponding to at least a part of the detected plurality of interference signals;
Interference suppression means for suppressing a plurality of interference signals included in the received signal in the first frequency band by subtracting a plurality of interference replica signals corresponding to the plurality of interference signals from the received signal in the first frequency band; Prepared,
The interference replica signal generation means and the interference suppression means so that processing including detection of the plurality of interference signals, generation of the plurality of interference replica signals, and suppression of the plurality of interference signals is executed a plurality of times in succession. A base station comprising a plurality of sets. In the base station of claim 1,
A base station comprising two sets of the interference replica signal generation means and the interference suppression means. In the base station according to claim 1 or 2,
The base, wherein the detection of the plurality of interference signals, the generation of the plurality of interference replica signals, and the suppression of the plurality of interference signals are successively performed a plurality of times in order of increasing strength of the plurality of interference signals. Bureau. In the base station according to any one of claims 1 to 3,
The interference replica signal generation means calculates values of a plurality of parameters necessary for generating the interference replica signal that can be calculated from the reference signal and the received signal of the first frequency band, and the calculated values of the plurality of parameters Generating the interference replica signal based on the base station. In the base station of claim 4,
The base station characterized in that the parameters used for generating the interference replica signal are a frequency offset, a delay time, and an amplitude of the interference signal. The base station of claim 5,
The interference replica signal generation means includes
Calculating a correlation value between the reference signal and the received signal in the first frequency band while setting a plurality of sets of frequency offset, delay time and amplitude for the reference signal;
A base that estimates the frequency offset, delay time, and amplitude of the interference signal by comparing a correlation value calculated for each of the plurality of combinations of the frequency offset, delay time, and amplitude with a preset threshold value Bureau. The base station of claim 5,
The interference replica signal generation means includes
Based on an offset reference signal in which the frequency offset and delay time are set in the reference signal and a weight corresponding to the amplitude, the interference replica signal is generated,
The weight difference is calculated based on the difference between the received signal in the first frequency band and the interference replica signal and the offset reference signal, and the weight is updated using the difference. base station. In the base station according to any one of claims 4 to 7,
Storage means for storing the estimated value of the parameter;
The base station characterized in that the interference replica signal generation means generates the interference replica signal based on the value of the parameter stored in the storage means and the reference signal of the first frequency band. The base station of claim 8,
Update means for repeatedly updating the estimated value of the parameter stored in the storage means at a predetermined timing;
The base station characterized in that the update timing can be changed. In the base station according to any one of claims 1 to 9,
The path of the received signal received by the first receiving means is a first path where interference signal suppression processing is performed by the interference suppression means, and a second path where interference signal suppression processing is not performed by the interference suppression means. A base station characterized by comprising reception path switching means for switching between and. The base station of claim 10,
Control means for controlling the reception path switching means to switch the path of the reception signal from the first path to the second path when the intensity of the reference signal is equal to or less than a threshold value or less than a threshold value; A base station characterized by that. In the base station according to any one of claims 1 to 11,
The received signal of the first frequency band includes a plurality of interference signals having different frequency offsets, delay times, and amplitudes from each other. In the base station according to any one of claims 1 to 12,
The first frequency band radio signal received by the first receiving means is a 1.5 GHz band radio signal transmitted from the communication terminal,
The base station, wherein the second frequency band radio signal received by the second receiving means is an 11 GHz band radio broadcast signal transmitted from a broadcast satellite. In the base station according to any one of claims 1 to 13,
The interference signal included in the first frequency band radio signal received by the first receiving means is at least a frequency converter that converts a radio broadcast signal into an intermediate frequency signal and an amplifier that amplifies the intermediate frequency signal. A base station characterized by a leaked signal leaked from one device. By subtracting the interference replica signal corresponding to the interference signal from the reception signal of the first frequency band including the desired signal transmitted from the communication terminal and the interference signal that interferes with the desired signal, reception of the first frequency band is performed. An interference suppression device for suppressing an interference signal included in a signal,
When receiving a radio signal in the first frequency band including the desired signal and a plurality of interference signals that interfere with the desired signal, the second frequency before frequency conversion to the interference signal in the first frequency band Reference signal generating means for receiving a radio signal in the second frequency band from a radio receiving device that receives a radio signal in the band, and generating a reference signal in the first frequency band by converting the frequency of the received signal in the second frequency band When,
The received signal of the first frequency band is input, and based on the reference signal and the received signal of the first frequency band, a plurality of interference signals included in the received signal of the first frequency band are detected and detected. Interference replica signal generating means for generating a plurality of interference replica signals corresponding to at least a part of the plurality of interference signals, and a plurality of interference replica signals corresponding to the plurality of interference signals from the received signal in the first frequency band Interference suppression means for suppressing a plurality of interference signals included in the received signal of the first frequency band by subtracting,
The interference replica signal generation means and the interference suppression means so that processing including detection of the plurality of interference signals, generation of the plurality of interference replica signals, and suppression of the plurality of interference signals is executed a plurality of times in succession. An interference suppression apparatus comprising a plurality of sets. By subtracting the interference replica signal corresponding to the interference signal from the reception signal of the first frequency band including the desired signal transmitted from the communication terminal and the interference signal that interferes with the desired signal, reception of the first frequency band is performed. An interference suppression method for suppressing an interference signal included in a signal,
When receiving a radio signal in the first frequency band including the desired signal and a plurality of interference signals that interfere with the desired signal, the second frequency before frequency conversion to the interference signal in the first frequency band Receiving a radio signal of the band;
Generating a first frequency band reference signal by frequency-converting the received signal of the second frequency band;
Based on the reference signal and the received signal in the first frequency band, a plurality of interference signals included in the received signal in the first frequency band are detected and corresponding to at least a part of the detected plurality of interference signals Generating a plurality of interference replica signals;
Subtracting the plurality of interference replica signals from the received signal of the first frequency band,
A method for suppressing interference, wherein the steps of detecting the plurality of interference signals and generating a plurality of interference replica signals and the step of suppressing the plurality of interference signals are successively executed a plurality of times.

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